Most of the documents are generated in an instant, plus we deployed this on Kubernetes with HPA, so high load isn't an issue.
The main issue I found with an HTML-based approach is that browsers are not designed for papers. It would be very challenging, but still possible [1], to customize the page layout, headers, and footers. Nonetheless, we have even more advanced use cases that only Typst/LaTex could cater to, such as displaying the table header of a table that spans multiple pages on every page.
[1] https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_media_q...
The team I'm currently working with are using Gotenberg for things which we can afford to take a little while, and C#/Skia for things which need to be reasonably quick.